If you're Sumlin there's no reason to go to Texas though - he's got the best possible situation he could have as a college coach right now. A possible bump in pay really isn't that big a deal, I'd be willing to bet, as compared to the ability to play in (and recruit for) the SEC.
The only thing that would draw him away from A&M currently might be the NFL, if he thinks his system could be successful there. I'd bet he's got a close eye on the Chip Kelly experiment in Philly to see how it works out.
And I see no incentive for Saban to want to move to Austin either, for that matter. What's his incentive? He's at an age where he's got a perfect system in place, making more than plenty of money, and will be legendary in Alabama just like Bear Bryant. He won't be able to replicate that in Austin in the Big 12, and surely that weighs on his mind.
Texas needs an up and coming coach that's currently a coordinator somewhere, or a coach that's been very successful at a smaller program, and is hungry and ready to make the step up to a big time program that he can build - in that sense I agree with ABQCowboy.